Pillared and Reduced Graphene Oxide Membranes for Organic Solvent Nanofiltration

This work demonstrates the capability of pillared and reduced graphene oxide (GO) membranes to perform organic solvent nanofiltration (OSN) in diverse nonpolar and polar solvents. The effects of pillaring by polyconjugated aromatic compounds (PACs) on solvent flux and molecular weight cutoffs (MWCOs) are investigated. Pyranine/solvent green 7 (SG) and toluidine blue O (TBO) were used as pillaring agents, followed by chemical reduction with hydriodic acid. This fabrication process yielded membranes with a stable cross-flow operation in both polar and nonpolar solvents. Pillared and reduced membranes (rSG-GO and rTBO-GO) exhibited 2-fold higher permeances in nonpolar solvents (C₆-C₁₀ alkanes and aromatics) compared to nonpillared membranes, while maintaining MWCOs of 500-600 Da in toluene. The membranes broadly followed a trend of higher permeance with decreasing solvent viscosity but with nuanced deviations based on membrane-solvent interactions. Reducing the thickness to ∼70 nm further enhanced permeance while maintaining rejection of larger solutes.